34 



DEVELOPMENT OF THE FROG'S EGG 



[Cn. IV 



If a series of sections be made through the egg at different 

 stages in the process of cleavage, we should see that prior to 

 the division of each blastomere the nucleus had divided into 

 two parts. This takes place by the ordinary process of indirect 



D 



FIG. 13. Segmentation of egg (two, eight, sixteen, and thirty-two cell stages, after 

 M. Schultze), as seen from above. A. Two-cell stage; beginning of second fur- 

 rows. B. Eight-cell stage, with cross-furrow. C, D, F, G. Sixteen-cell stages. 

 E. Eight-cell stage (regular type). H. Thirty-two-cell stage. 



or karyokinetic division. Half of the chromatin passes to one 

 pole of the nuclear spindle, and the other half to the other pole. 

 As the spindle elongates, it carries with it the surrounding pig- 



